Compounds having 2-nitroimidazole as parent nucleus show high orientation toward hypoxic cancer cells, and have an excellent action of reoxygenating hypoxic cancer cells due to the high electron affinity of the nitro group. Thus, investigations have been extensively conducted on the use of such characteristics in cancer radiotherapy in relation to hypoxic cancers having radiation resistance. Particularly, if a side chain of 2-nitroimidazole has an acyclic sugar chain structure, it is known that the corresponding compounds have features of being easily metabolized and excreted, and being available within cancer cells when exposure to radiation is needed, while being rapidly excreted out of the body after completion of radiation treatment, thus the compounds being highly useful (see, for example, Patent Documents 1 to 3). However, introducing an acyclic sugar chain structure leads to the introduction of a large number of reactive hydroxyl groups, and thus is also accompanied by a demerit such as that a number of processes for protection and deprotection of such hydroxyl groups must be undertaken, and more time is required in the production.
Thereafter, it was also found, as a characteristic of 2-nitroimidazole derivatives, that the derivatives have a property of readily orienting themselves at hypoxic sites, without being limited to cancer sites. Thus, discovery was made on the use of the derivatives as imaging agents for hypoxic sites, by introducing 18F as a radioisotope into a side chain of such a derivative, and visualizing the location of presence of the derivative inside the body using positron emission tomography (PET) (see, for example, Patent Documents 4 and 5). However, in the case of introducing such a radioisotope, if the derivative has the previously mentioned acyclic sugar chain structure in the side chain, the operations of protection and deprotection of hydroxyl groups must be repeated, and thus degradation of the compound frequently occurred during the time of such operation, and the final yield was also unavoidably lowered. Upon considering the scarcity value of 18F, it can be said that circumstances such as described above definitely bring forth large losses.
Meanwhile, in regard to the introduction of an acyclic sugar chain, attempts have been made to bring an improvement even in terms of the difficulty in production (see, for example, Patent Documents 6 and 7), but a method suitable for producing such a derivative having a radioisotope has not yet been found.    [Patent Document 1] JP-A-06-279415    [Patent Document 2] JP-A-03-223258    [Patent Document 3] JP-A-01-110675    [Patent Document 4] Japanese kohyo Patent Publication No.    [Patent Document 5] Japanese kohyo Patent Publication No. [Patent Document 6] JP-A-02-48549    [Patent Document 7] JP-A-06-228123